The tools make it easier for developers to use the data on separate applications, increasing interoperability among platforms, Microsoft said. Including those not controlled by Microsoft.

“Customers are telling us they need greater interoperability,” William Kennedy, Microsoft’s corporate vice president for Office Communications and Forms, said in an announcement, “and we believe that welcoming competition and choice will create more opportunities for customers, partners and developers.”

And competitors. Throughout the open-sourcing process, some have wondered why Microsoft is opening up the file format now.

Because opening the .pst format makes it easier for Google and others to attract customers who might have been squeamish about transitioning from Outlook and Exchange to Gmail. Without deep interoperability, transitioning can be difficult when dealing with thousands of pieces of data, many of which must be stored to comply with regulations.